1. Field of the Invention
The present invention relates to a current sensor that measures a current flowing in a conductor while eliminating the influence of a disturbance magnetic field.
2. Description of the Related Art
Since a relatively large current is handled in a motor driving technology field such as in an electric vehicle, a hybrid car, or the like, there is a demand for a current sensor capable of measuring such a large current without contact. Such a current sensor is mounted in, for example, a three-phase motor having three current paths which are arranged in parallel with each other. In the current sensor mounted in such a three-phase motor, it is necessary to prevent deterioration of measurement accuracy of a current to be measured by suppressing the influence of a magnetic field generated by a neighboring current flowing in a neighboring current path that is disposed adjacent to a current path to be measured.
As such a current sensor, there has been proposed a current sensor that may eliminate the influence of a disturbance magnetic field by performing a differential processing with respect to output signals of two magnetic sensing elements. For example, in a current sensor of U.S. Pat. No. 6,512,359, a through-hole is formed in a middle portion of a current path to thereby enable a current to be separated into two of first and second current paths, a first Hall element for detecting a disturbance magnetic field is provided in the through-hole, and a second Hall element for measuring a current (for detecting a signal) is provided outside the first current path and the second current path. In this case, magnetic fields of the first and second current paths offset each other in the first Hall element provided in the through-hole, and therefore the first Hall element outputs an electric signal corresponding to the intensity of the disturbance magnetic field. Therefore, by performing a differential process with respect to an output signal of a first magnetic sensing element and an output signal of a second magnetic sensing element, it is possible to measure a current value flowing through the current path while eliminating the influence of the disturbance magnetic field.
However, in the above-described current sensor, in a case in which the disturbance magnetic fields in different directions are applied to the first Hall element for detecting the disturbance magnetic field and the second Hall element for measuring a current, a current cannot be accurately measured. In particular, in a case in which a neighboring current path that is disposed adjacent to a current path to be measured exists, due to the influence of the neighboring current path, a current value of the current path to be measured cannot be accurately measured. In addition, in a case in which a large current flows in the current path to be measured, it is necessary to form a wide current path, but in a case in which the wide current path is formed, it is difficult to transform the current path (to separate the current path into two).